Lipo

[RC-Monster Mike]

LiPo are either expensive or cheap, depending on how you look at it. If you think about them in a similar way to thinking about brushless. The up front cost may be a little higher than other options, but the long term costs will be a lot lower (brushless motors last a lot longer than brushed motors with no maintenance cost either - LiPos batteries have more power, less weight and are capable of up to ten times the number of cycles than a nicad/nimh battery is capable of).